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Thoughts on 3M max tails protection with SPD & isolator in tails?

justinneedham
DNO allowance for tails protection from their fuse is commonly 3M. - 3M is deemed AFAICT to extent through any in-line isolator, whether or not that isolator is property of DNO or is consumer fitted part. (The latter is not spelled out by DNO SSEPD who  just state the 3M tails figure without further qualification).
If said isolator begins to sprout additional complexity such as MCB and SPD as a shunt addition, my interpretation (Definitions, part 2) is that it still doesn’t yet qualify as a consumer unit, hence the 3M rule could be said to still run straight through it as far as the farthest CU.

- Any thoughts?

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    Is the '3m tails' in SSEPD territory written in stone, or is it subject to interpretation? We have been asked to do an EICR on an installation, and the first thing I noticed is that the CU is at the opposite end of the garage from the intake. The tails are circa 6m in length and enclosed in 25x40 minitrunking.  I suspect the Ze and PFC are still sufficient to take out the 60A service cutout but it did look odd to me.


    Edit: the service is 60A, there's a sticker to the effect on the main fuse carrier, and the fuse has not been 'unsealed'. The tails are 25mm2, both from head to meter, and from meter to CU, no REC isolator present. The meter is NOT the type with the load terminals accessible without removing a seal, so it must have been sealed with those tails in place
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  • 0
    Is the '3m tails' in SSEPD territory written in stone, or is it subject to interpretation? We have been asked to do an EICR on an installation, and the first thing I noticed is that the CU is at the opposite end of the garage from the intake. The tails are circa 6m in length and enclosed in 25x40 minitrunking.  I suspect the Ze and PFC are still sufficient to take out the 60A service cutout but it did look odd to me.


    Edit: the service is 60A, there's a sticker to the effect on the main fuse carrier, and the fuse has not been 'unsealed'. The tails are 25mm2, both from head to meter, and from meter to CU, no REC isolator present. The meter is NOT the type with the load terminals accessible without removing a seal, so it must have been sealed with those tails in place
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